Ilana Doran
Advisor: Dr. Navdeep Panesar
Project Title: Birth and Evolution of a Jet-Base-Topology Solar Magnetic Field with Four Consecutive Major Flare Explosions
Project Description:
During 2011 September 6-8, NOAA solar active region (AR) 11283 produced four consecutive major coronal mass ejections (CMEs) each with a co-produced major flare (GOES class M5.3, X2.1, X1.8, and M6.7). We examined the AR’s magnetic field evolution leading to and following each of these major solar magnetic explosions. We follow flux emergence, flux cancellation and magnetic shear buildup leading to each explosion, and look for sudden flux changes and shear changes wrought by each explosion. We use AIA 193 Å images and line-of-sight HMI vector magnetograms from Solar Dynamics Observatory (SDO), and SunPy, SHARPkeys, and IDL Solarsoft to prepare and analyze these data. The observed evolution of the vector field informs how magnetic field emergence and cancellation lead to and trigger the magnetic explosions, and thus informs how major CMEs and their flares are produced. We find that (1) all four flares are triggered by flux cancellation, (2) the third and fourth explosions (X1.8 and M6.7) begin with a filament eruption from the cancellation neutral line, (3) in the first and second explosions a filament erupts in the core of a secondary explosion that lags the main explosion and is probably triggered by Hudson-effect field implosion under the adjacent main exploding field, and (4) the transverse field suddenly strengthens along each main explosion’s underlying neutral line during the explosion, also likely due to Hudson-effect field implosion. Our observations are consistent with flux cancellation at the explosion’s underlying neutral line being essential in the buildup and triggering of each of the four explosions in the same way as in smaller-scale magnetic explosions that drive coronal jets.
Tiger Du
Advisor: Dr. Vladimir Florinski
Project Title: Deconvolution of the Energetic-Particle Count Rates of Voyager 1 and Voyager 2 to Identify the Causes of Dropouts and Enhancements and to Characterize the Structure of the Heliopause
Project Description:
The Voyager spacecraft are the only spacecraft to make direct measurements of the heliopause, where the solar wind and the interstellar wind are in equilibrium. Therefore, analyzing these Voyager measurements is important to our understanding of this region. Of special interest in this research are anomalies in the energetic-particle count rates measured by the Low-Energy Telescopes (LETs) of Voyager 1 (V1) and Voyager 2 (V2) around the heliopause; V1 observed two dropouts just before its crossing of the heliopause in August 2012, and V2 observed two enhancements just after its crossing of the heliopause in November 2018. We analyze these signals by deconvolution to identify the physical causes of these anomalies, which are hypothesized to be either A) magnetic flux tubes between the heliosheath and the very local interstellar medium (VLISM) or B) the motion of the heliopause itself. Prior to deconvolution, the signals are processed by 1) nonlinear least squares polynomial curve fitting to decrease the effect of low-period noise and, for the dropouts only, 2) reflection about a horizontal axis to better condition the deconvolution since this operation is not well behaved at the extremities of signals. An additional processing operation that is being explored for use in this analysis is differentiation. To deconvolve the Voyager signals, we use a nonnegative least squares (NNLS), total variation diminishing (TVD) solver. Preliminary results of the time delays between the V1 signals during its first dropout agree with those from visual inspection. Further analysis based on the computed time delays, the sightlines of the LETs of V1 and V2, the measured magnetic field directions, and the width of the intensity transitions will result in 1) identification of the physical causes of the measured anomalies in energetic-particle count rates, 2) the radial velocity of the plasma around the Voyagers as they crossed the heliopause, and 3) the widths of the structures that caused the anomalies. In summary, this study contributes to our understanding of the structure of the heliopause and demonstrates for the first time in the field of space plasma physics the successful application of deconvolution to time delay estimation.
Alexis Lupo
Advisor: Dr. Peter Jenke
Project Title: Building Gamma-Ray Detectors for Two CubeSats
Project Description:
Terrestrial RaYs Analysis and Detection (TRYAD) is a collaborative project between The University of Alabama in Huntsville, Auburn University, and NASA Goddard Space Flight Center that focuses on the development of two CubeSats to detect and measure Terrestrial Gamma-ray Flashes (TGFs). TGFs are short bursts of gamma-radiation in the upper atmosphere thought to be associated with Bremsstrahlung radiation originating from electrons accelerated in thunderstorms. The two CubeSats will be deployed in low-Earth orbit, flying in tandem, and taking multipoint measurements of the TGF beams to shed insight into their production mechanisms. The primary roles of UAH in the TRYAD mission include creating the Science Instrument Package (SIP) which will act as the gamma-ray detector of the CubeSats and to design the Data Acquisition (DAQ) board that powers and reads data from the SIP. Recent work has been focused on testing and assembling the first SIP to prepare for a launch planned for 2023.
Syed Raza
Advisor: Dr. Nikolai Pogorelov
Project Title: Constraining CME Models using STEREO data for Space Weather Predictions
Project Description:
In this work, we constrain the kinematics of our MHD coronal mass ejection (CME) model with multiple viewpoints of STEREO coronagraph and heliospheric imager (HI) data to improve the arrival time predictions. We show our approach using the 12 July 2012 CME. Using the kinematics derived from coronagraph observations using the graduated cylindrical shell (GCS) model, we simulated a flux-rope-based CME. By comparing simulations and observations of this event at Earth, we found that our simulated CME arrived ~2.5 hours after the observed CME. To compare the evolution of our simulated CME with observations in the inner heliosphere, we created synthetic J-maps from our simulation data and compared them with the J-maps created from STEREO HI observations. By comparing the time-elongation angle graphs extracted from the synthetic and observed J-maps, we found that on average our simulated CME was trailing the observed CME by 2 hours in both STEREO A and B. Offsetting this time from the arrival time of our simulated CME reduces the arrival time prediction error to just 0.5 hour. Therefore, constraining MHD models with HI observations has the potential to improve the arrival time predictions. This approach will be validated by performing simulations of multiple other CMEs as a future work.
Santiago Rodriguez
Advisor: Dr. Jakobus A. le Roux
Project Title: Investigation of Superdiffusive Energetic Particle Transport Ahead of Traveling Shocks
Project Description:
We investigated the connection between the shape of energetic particles' time-intensity profiles ahead of collisionless interplanetary shocks driven by coronal mass ejections and anomalous diffusion. Three strong shocks were recently studied by Zimbardo, Prete, and Perri (2020). They found mostly superdiffusive behavior characterized by: (i) More energetic particles are more superdiffusive and, (ii) energetic particles ahead of shocks with larger shock normal angles (θ) are less superdiffusive.
Ayla Weitz
Advisor: Dr. David Falconer
Project Title: Characterizing the Time Evolution of Free-Energy Proxies to Forecast West Limb Flares, CMEs, and SEPs
Project Description:
Predicting an active region’s (AR) tendency to produce major flares, coronal mass ejections (CMEs), and Solar Energetic Particle events (SEPs) is essential for ensuring astronaut safety. MagPy’s predictions are derived from free-energy proxies from HMI vector magnetograms. To better forecast eruptions from regions far from disk center, most notably the west limb, we want to accurately predict free-energy proxies several days into the future. Due to projection effects, we show magnetic measures in JSOC deprojected cylindrical magnetograms are over-estimated as a function of distance from disk center. We use approximately 600 large-flux ARs (total magnetic flux > 1022 Mx) and normalize each measure by dividing by the AR’s measure value when it is closest to central meridian. Using a Chebyshev fit, we are able to characterize each measure’s dependence on degree distance from disk center, and correct for this error by dividing the data by the fit value at the corresponding distance. Applying the correction to all values, the corrected data shows essentially no dependence on radial distance. We determine that a correction must be used to more accurately predict AR free-energy proxies west of central meridian. With the corrected data, we investigate multiple methods of using observations of eastern longitudes to predict the west for a variety of lead times. In order to determine how well a method predicts, we construct histograms of the ratios of observed values to values the model gives. We fit third order gaussians to the histograms and conclude that the most accurate method should minimize the second order term (standard deviation). Preliminary results show persistence to be the best predictor for short lead times.
Lucy Wilkerson
Advisor: Dr. Sanjiv Tiwari
Project Title: Characterizing Steady and Bursty Coronal Heating of a Solar Active Region
Project Description:
One of the biggest problems in solar physics today is our inability to explain why the solar corona is so hot. In this project, we aimed to quantify transient and background coronal heating for a given active region in order to better understand coronal heating. We used SDO/AIA data of the active region NOAA 12712 observed on May 29, 2018 over a period of 24 hours with a 3-minute cadence. We calculated FeXVIII emission (hot component of AIA 94 Å channel) by removing warm components using AIA 171 and 193 Å channels. From the maximum, minimum, and mean brightness values of each pixel over the full 24-hour period, we made maximum, minimum, and mean brightness maps. We repeated this process in moving time windows of 16 hours, 8 hours, 5 hours, 3 hours, 1 hour, and 30 minutes. We used the total luminosity for each of these maps over time to make lightcurves that show the evolution of maximum, minimum, and mean brightness over time for each running window. Finally, we took the ratio of the total maximum and total minimum luminosity to total mean luminosity, and plotted these ratios over time. The average maximum to mean ratio was 8.40±0.00, 6.36±0.46, 5.29±0.34, 4.73±0.24, 4.19±0.19, 3.21±0.17, and 2.64±0.15 and the average minimum to mean ratio was 0.053±0.00, 0.08±0.00, 0.12±0.01, 0.14±0.02, 0.17±0.02, 0.26±0.02, and 0.33±0.03 for 24h, 16h, 8h, 5h, 3h, 1h, and 30m windows, respectively. As expected, the ratio of background to mean luminosity increased as the time window decreased, and the ratio of transient to mean luminosity decreased as the time window decreased. As such, the ratio of background to mean luminosity is a new and effective technique to quantify the background intensity of the active region. Our 24h window result suggests that at most 5% of the luminosity of the AR at a given time comes from the steady background heating. This upper limit increases to 33% of the luminosity of the AR for the 30 min running window.
Reese Williams
Advisor: Dr. Amy Winebarger
Project Title: Optimizing a Machine Learning Algorithm for the Development of Future Instrumentation
Project Description:
One of the most outstanding questions to be answered in solar physics deal with extracting the density measurements of plasma in coronal mass ejections (CMEs). Access to this data could provide crucial information about energy fluctuations in CMEs. The COronal Spectroscopic Imager in the EUV (COSIE); is a slitless imaging spectrometer designed to observe CMEs over an extended field of view. Imaging spectrographs provide useful data corresponding to temperature, density, and abundance of certain elements. Although useful data is provided, the larger field of view of this instrument makes analyzing the data difficult due to the spatial and spectral convolution confusion. In slitless spectrometers, the spatial and spectral data gets convolved together and displayed as an overlappogram image, meaning the image contains many spectrally pure images of the sun that are overlapped with each other. The overlapping makes the data difficult to understand. It is, therefore, necessary to unfold the overlapped data in order to isolate the contributions from the individual elements. The proposed method for the COSIE unfolding process requires a machine learning algorithm to interpret the data. A previous project verified that this algorithm worked for on-limb event such as flares and determined the best optimal parameters for the instrument when observing that event. In our project, we will investigate how accurate the unfolding algorithm is for an off-limb, dim CME. We will also determine the best optimal parameters for the proposed instrument when viewing these types of events.
Hind Zeitohn
Advisor: Dr. Michael Briggs
Project Title: Finding Fast Gamma-ray Variability in Solar Flares
Project Description:
Fast Radio Bursts (FRBs) are fast, bright, extragalactic transients, typically associated with magnetars. In early 2021, a very sensitive radio array observed a unique FRB-like event which localized to the Sun. This solar-FRB (sFRB) lasted for only a few milliseconds at 1.4 GHz and had a flux density of 9.1 Mega-Janskys (910 solar flux). This millisecond long sFRB was seen as a 'spike' in the radio data, which raises the question, can sFRBs be detected in other wavelengths? Fermi-GBM has a 4 pi steradian field of view of the sky and measures gamma-rays down to 2 microseconds temporal resolution, which makes it the perfect instrument for detecting sFRBs. If such variability were to be found in the Fermi-GBM data, it would provide evidence that this unique energetic process spans multiple 9 orders of magnitude in energy. We performed a blind search of Solar Flares in the Fermi-GBM time-tagged event (TTE) data, binned at 10, 20, and 50 milliseconds in the 5 keV to 20 keV range starting from November 27th, 2012, and ending on April 23rd, 2021. Of the ~3500 solar flares that were examined, no statistically significant gamma-ray emission were detected. We derive upper limit density flux range for the gamma-ray emission to be 0.2 to 0.9 Janskys.
Benjamin Zigament
Advisor: Dr. Alphonse Sterling
Project Title: Studying Solar Active-Region Magnetic Evolution Leading to a Confined Eruption
Project Description:
Current research suggests that there exists a continuum of solar eruptions ranging from the comparatively small, such as coronal jets, to extremely large eruptions that produce coronal mass ejections (CMEs) and solar flares, with all sharing a common triggering mechanism: a filament/flux rope eruption triggered by magnetic flux cancellation. For coronal jets the erupting 'minifilaments' are of length ~10,000 km (Sterling et al. 2015, Panesar et al. 2016), while the larger eruptions are accompanied by eruptions of typical filaments of size ~several x 10^4 --- ~3x10^5 km. Sterling et al. (2018) examined this idea for two small ARs (flux ~ 2x10^21 Mx) that erupted to make CMEs. They tracked the evolution of the ARs from emergence to eruption and found eruption to occur when some of the emerged flux drifted together and underwent cancellation along the main magnetic neutral line on the interior of the AR, with eruption occurring after about 30---50% of the total flux of the respective regions canceled. Here we perform a similar study, using Solar Dynamics Observatory (SDO) AIA EUV images and SDO/HMI magnetograms, of a smaller AR (total flux <~10^21 Mx) that emerged in isolation near the neutral line in a large overarching old weak-field magnetic arcade on 2014 September 8. It produced a confined eruption (i.e., one that did not make a CME) about three days later, on September 10 near 18:45 UT. The AR’s flux reached maximum about 12 hr after emergence start, and then decreased continuously, with the decrease being partly from cancellation of small flux clumps in the interior of the AR. The eruption occurred when the flux had decreased by about 20%, and was centered on the neutral line of the emerged AR, but also involved filament-holding field along some of the old arcade’s neutral line. That filament underwent a confined eruption as part of the overall confined eruption. The emerged AR’s being inside the larger arcade, its smaller size, and its smaller amount of cancellation may be reasons why the eruption was confined, instead of being ejective and producing a CME as in the two cases of Sterling et al (2018).
